1. Field of the Invention
The present invention generally relates to a disk device. More specifically, the present invention relates to a disk device having a cam mechanism for lifting a traverse chassis.
2. Background Information
With a conventional disk device, one end of a traverse chassis is supported by a stationary-side frame (loader chassis). The traverse chassis is capable of inclined movement (up-and-down movement) along a linear path, in which a support position of the stationary-side frame serves as the fulcrum. Also, in addition to an optical pickup and other such optical elements, a turntable is installed on the traverse chassis. When the traverse chassis moves along with the turntable, a disk that has been placed on the turntable is clamped by a joint action of the turntable and a damper that is attached to the stationary-side frame and waits at a specific location. The disk clamped by the damper and the turntable rotates along with the turntable. During the rotation, the disk is optically processed by the optical pickup (see Japanese Laid-Open Patent Application Publication No. 2007-172787, for example).
When an off-center disk is subjected to optical processing, the offset in the center of gravity of the disk rotating along with the turntable causes self-induced vibration. The self-induced vibration can decrease the positional stability of the traverse chassis on which the optical pickup is mounted. In view of this, a variety of measures has been adopted in the conventional disk devices to improve the positional stability of the traverse chassis.
One such measure is to divide the traverse chassis into a chassis main body and an auxiliary member (lever shift) that is shorter in a longitudinal direction than the chassis main body. The chassis main body is made from sheet metal, which increases the weight of the traverse chassis. Furthermore, a rear end part of the chassis main body (corresponds to one end of the traverse chassis) is supported on the stationary-side frame via a first cushioning member that has a damping action. The auxiliary member, which is made from plastic, is linked to the chassis main body via a second cushioning member. The effect of employing this measure is that the weight of the traverse chassis is increased over that when the traverse chassis is made from plastic. Thus, the traverse chassis is less likely to vibrate, and the positional stability of the traverse chassis is increased. Also, the first cushioning member is interposed at the place where the stationary-side frame is linked to the rear end part of the chassis main body of the traverse chassis, and the second cushioning member is interposed at the place where the auxiliary member is linked to the chassis main body. Thus, the damping actions of the first and second cushioning members will help improve the positional stability of the traverse chassis.
Another measure is to modify the configuration of a cam mechanism for tilting (reciprocally moving) the other end of the traverse chassis along the linear path by using the support position of the stationary-side frame as a fulcrum.
The cam mechanism has a follower, a cam plate, a cam groove and an auxiliary guide member. The follower is provided to the auxiliary member. The cam plate is moved leftward and rightward in a direction perpendicular to a direction of the up-and-down movement of the other end of the traverse chassis. The cam groove is provided to the cam plate. The follower slides in the cam groove to move the other end of the traverse chassis (the front end part of the auxiliary member) in the direction of the up-and-down movement along the linear path. The auxiliary guide member slides the follower when the cam plate moves leftward and rightward and has a straight guide face that guides the up-and-down movement of the follower. The cam groove of the cam plate is equipped with a first ride face on which the follower rides up at a limit of the rightward movement, a second ride face on which the follower rides up at a limit of the leftward movement, and an inclined face that connects the first and second ride faces.
With the conventional disk device having the cam mechanism, when the damper and the turntable installed on the traverse chassis jointly clamp the disk, the follower that has ridden up onto the first ride face of the cam groove is located within the cam groove and is guided by the guide face. Furthermore, the pressing action in a leftward direction of a plastic spring provided to the auxiliary guide member causes the follower to be pressed elastically at a right angle in the leftward direction against the guide face of the auxiliary guide member. Accordingly, the follower and the other end of the traverse chassis equipped with the follower are positioned in the leftward and rightward directions of the traverse chassis.
With the cam mechanism, in order to minimize the decrease in the positional stability of the traverse chassis by the self-induced vibration attributable to deviation in the center of the gravity of the disk, it is preferable for the follower of the cam mechanism that has ridden up onto the first ride face of the cam groove to be flanked by the cam groove and the guide face, and to be accurately positioned in the mutually perpendicular directions.
However, there is a gap attributable to production error, or a gap that is essential in terms of permitting smooth movement of the follower, or another such gap between the cam groove and the follower of the cam mechanism that has ridden up onto the first ride face of the cam groove. Thus, even though the follower is elastically pressed by the plastic spring against the guide face, the follower is not positioned accurately and without any looseness in the direction of the up-and-down movement of the traverse chassis. Accordingly, with the cam mechanism, the self-induced vibration during the disk rotation is transmitted to the follower, and the follower vibrates. As a result, optical read error tends to occur in the optical pickup, which causes image distortion, sound jump, and the like.
This problem is especially apt to occur when playing a disk whose center of gravity is off-center. Also, there is the risk that the guide face of the auxiliary guide member, the first ride face of the inclined face will be deformed by heat generated by the vibration of the follower, which would make optical read errors more likely to occur. This is much more likely to happen under a high-temperature environment (a temperature of 65° C. and a humidity of 80%), or after high-temperature storage (storage for 120 hours at a temperature of 65° C. and a humidity of 80%).
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved disk device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.